Fluorescent pipettes for optically targeted patch-clamp recordings

Targeted patch-clamp recordings are a promising technique that can directly address the physiological properties of a specific neuron embedded in a neuronal network. Typically, neurons are visualized through fluorescent dyes or fluorescent proteins with fluorescence microscopy. After switching to transmitted light microscopy, neurons of interest are re-identified and visually approached in situ with patch-clamp pipettes. Here we introduce a simpler method for neuron targeting. With fluorophore-coated pipettes, fluorescently labeled neurons and the pipette tips are simultaneously imaged at the same fluorescence wavelength in the same microscope field, so that the neurons and even their neurites are targeted without suffering from chromatic aberration or mechanical complication in optics. We did not find that the coated fluorophores affected the electric properties of pipettes or neurons. The novel technique will be wildly available for pipette micromanipulation under online visual control.